SSRIs, SNRIs and antipsychotics can affect how your body regulates heat. This may lead to increased sweating, heat intolerance, or a higher risk of overheating in hot weather.

Why do SSRIs, SNRIs and antipsychotics affect body temperature?

Some psychotropic drugs and heat regulation issues are linked to how these medicines act on the brain and body.

• Antipsychotics can reduce your body’s ability to cool itself. This increases the antipsychotics overheating risk, especially in warm environments.
• SSRIs and SNRIs (antidepressants) may cause excessive sweating, which is a common side effect related to temperature regulation.

Together, these changes can make it harder to cope with heat, leading to medication heat intolerance.

How antipsychotics affect temperature regulation

Antipsychotics are often used to treat conditions like schizophrenia and bipolar disorder.

They can:

• Interfere with the body’s natural cooling system
• Reduce awareness of heat or thirst
• Increase the risk of overheating on psychiatric medication

This means people taking them may find it harder to stay cool during a heatwave.

Read more to understand antipsychotic medication.

SSRIs, SNRIs and body temperature regulation

SSRIs (selective serotonin reuptake inhibitors) are widely used antidepressants. Examples include:

• Citalopram
• Fluoxetine
• Sertraline
• Paroxetine

SNRIs (serotonin-norepinephrine reuptake inhibitors) are similar to SSRIs and include:

• Duloxetine
• Venlafaxine

Common effects:

• Excessive sweating (a key sign of altered temperature control)
• Increased vulnerability to dehydration

Rare but serious risks:

• Serotonin syndrome – symptoms include sweating, fever, and shivering
• Hyponatraemia (low salt levels) – can affect how your body manages heat

Learn more about the side effects of antidepressants.

Can antidepressants cause heat exhaustion?

Yes, in some cases. Antidepressants and heat intolerance can increase the likelihood of:

• Heat exhaustion
• Dehydration
• Heat stroke (in severe cases)

This is more likely if you:

• Are older
• Take multiple medications
• Spend long periods in hot environments
  
  

Risks of overheating on psychiatric medication

During hot weather, SSRIs and body temperature regulation issues can combine with antipsychotic effects, increasing risk.

Key dangers include:

• Overheating due to reduced cooling ability
• Excessive sweating, leading to fluid loss
• Worsening mental health symptoms
• Reduced ability to recognise when you’re too hot
  
  

Are mood stabilisers affected by extreme heat?

Mood stabilisers like lithium are typically prescribed for bipolar disorder. They help prevent extreme emotion highs (mania) and extreme emotional lows (depression). 

Lithium must be monitored closely in a heatwave because:

• Dehydration through sweat and lack of water increases salt levels
• If lithium levels are too high you are more vulnerable to lithium toxicity
• Serious lithium toxicity can become life-threatening
  
  

Symptoms of lithium toxicity include:

• Feeling sick
• Stomach issue or diarrhoea
• Blurred vision
• Increased need to urinate
• Light-headedness, confusion, blackouts
• Difficulty speaking 
  
  

If you experience any of these symptoms, call 999 or go straight to A&E. 

Staying cool on mental health medication during summer

Simple steps can help you manage medication heat intolerance:

• Drink small amounts of water regularly
• Wear loose, light clothing
• Stay in the shade or indoors during peak heat
• Keep your living space cool (close curtains, open windows)
• Learn signs of heat exhaustion (dizziness, nausea, heavy sweating)

Read more about coping during a heatwave with mental illness.

When to seek help

Speak to your GP or healthcare professional if you notice:

• Severe or persistent sweating
• Feeling faint, confused, or unusually hot
• Symptoms of heat exhaustion or heat stroke

Important: Do not stop taking your medication without medical advice.

Key takeaways

• SSRIs and antipsychotics can affect body temperature regulation
• This can lead to sweating, dehydration, and overheating
• Risks are higher in hot weather or heatwaves
• Staying cool and hydrated is essential
  
  

Get support

If you’re worried about SSRI side effects, temperature regulation, or antipsychotics overheating risk, you’re not alone.

Visit the Rethink Mental Illness information and advice pages to understand more or speak to your GP if you need support.